I think the Korean can be translated in both the ways I did it above. In my friend's case, I think she was referring to the second translation.
살아온 세월만큼 아는 것이 인생인데.
- Life is what we learn along the way.
- Life is learning from our years of living.
- Life is what we know from our years of living.
Update: I have thought about it and think that Sentence 3 is the most accurate translation of the Korean.